1. Field of the Invention
This invention relates to a process for preparing fused fabrics. The invention also relates to apparatus for the production of fused fabrics. In another aspect, the invention relates to novel fused fabrics per se.
2. Description of the Prior Art
Thermoplastic fabrics are widely employed in furniture construction, civil engineering applications and the like. A common method employed to stabilize thermoplastic fabrics is to subject the fabric to conditions of heat and pressure sufficient to cause fusion of at least some of the fibers of the fabric. A problem with this procedure is that fabric strength of previously heat stabilized fabric as measured by ultimate strength and tear strength tests is usually reduced by subjecting the fabric to additional heat and pressure.
For some applications of thermoplastic fabrics, an embossed pattern impressed upon the fabric is desired. The embossing treatment compresses and densifies the fabric in the areas that are embossed. This treatment enhances the structural integrity and mechanical strength of the treated fabric.
In U.S. Pat. No. 4,135,024 there is disclosed an embossing process wherein a treating fluid is applied to the rear surface of a web simultaneously with the contacting of the web with an embossing roll. The web employed preferably includes over 50% by weight wood pulp fibers. Apparently fusion of the fibers in the web is not desired or accomplished since there is no disclosure of the application of heat in the embossing process.
U.S. Pat. No. 4,075,383 relates to a method for pattern bonding non-woven fabric made from polyamide filaments by treating the fabric with an acid activating agent and water vapor prior to passing the fabric between a pair of rolls, at least one of which is embossed and heated sufficiently to cause bonding of discrete portions of the fabric. The activating agents such as HCl, BF.sub.3, SO.sub.2 and the like are corrosive and undesirable chemicals to handle, yet are required to effect the desired bonding.
U.S. Pat. No. 3,454,413 describes a process for embossing a sheet material by printing a pattern on selected portions of the sheet material with a heat retarding liquid, then subjecting the printed sheet material to a heat source to cause areas unprotected by retarding liquid to become recessed in relation to protected areas. Thus, a mask or some means for selective application of heat retarding liquid is required such that fusion of the sheet material occurs only where heat retarding liquid has not been applied.
U.S. Pat. No. 4,134,948 deals with embossing a non-woven fabric comprising approximately 75% wood pulp fibers and 25% synthetic cellulose fibers by applying moisture to the batt, then passing the moistened batt through heated embossing rolls. Sufficient moisture is applied to insure good pattern definition. An embossing temperature of only 155.degree.-170.degree. F. is disclosed with further heating to drive off water and cure adhesive additive provided after adhesive application to the embossed batt.
U.S. Pat. No. 3,096,557 teaches passing of fabric wet with hot water (180.degree.-200.degree. F.) under pressure and at a temperature 10.degree.-200.degree. F. below the softening point of the synthetic polymer of the fabric between two confining rollers, one being a hard, rough-surfaced roller. Due to the temperatures employed, fabric fusion apparently does not occur.
U.S. Pat. No. 3,096,563 is similar to '557 discussed above. The temperature of the heated, rough-surfaced roll is specified to be 10.degree.-100.degree. F. below the softening point of the synthetic polymer of the fabric.
U.S. Pat. No. 4,306,929 describes a process for the preparation of point-bonded non-woven fabrics wherein thermally bondable fiber web containing an attenuating liquid is simultaneously heated and compressed in spaced, discrete areas. Only up to about 80% of the total surface area of the web is treated to heat and compression conditions. The function of the attenuating liquid is to prevent web fibers in the uncompressed areas of the web from reaching bonding temperatures. A point-bonded fabric of improved softness with no increase in fabric strength is said to be the result of such treatment.
U.S. Pat. No. 4,396,452 is similar to '929 discussed above. Autogenously bondable fiber web is specified and a point-bonded product of improved softness and increased fabric strength is said to result.
It is therefore an object of this invention to provide a process for the preparation of fused fabric. It is a further object of this invention to provide apparatus for the preparation of fused fabric. It is yet another object of this invention to provide fused fabrics per se. It is a further object of this invention to provide fused fabrics with increased strength, reduced thickness and a soft hand. It is yet another object of this invention to provide fused, embossed fabrics having improved pattern definition. It is yet another object of this invention to provide a non-woven fabric having a leather-like appearance.
These and other objects of our invention will become apparent from the disclosure and appended claims.